A blood pump assists the action of the heart of a patient whose circulatory system has failed. Therefore, if the function of the apparatus driving the blood pump stops, the patient will be adversely affected. If a perfectly artificial heart fails, then the function of the heart is completely lost. If an auxillary artificial heart or a balloon pump fails, burden is suddenly imposed on the patient's weakened heart.
Accordingly, the frequency of troubles in blood pumps and driving apparatuses must be reduced. To cope with troubles in driving apparatuses, various means have been proposed. An apparatus disclosed in Japanese Patent Laid-Open No. 136,352/1983 incorporates a battery and a pressure tank to make preparations for disconnection from an external power supply. An apparatus disclosed in Japanese Patent Laid-Open No. 207,668/1985 is equipped with a plurality of pressure sensors to monitor the waveform of pressure. In the techniques disclosed in Japanese Patent Laid-Open Nos. 169,463/1983 and 249,655/1987, two preessure-generating devices are mounted. If one of them fails, it can be switched to the other.
The prior art method of detecting trouble in a driving apparatus consists in detecting the output pressure, comparing the detected pressure with a preset pressure, and regarding the apparatus as defective if there is a great difference between them. For example, in the techniques desclosed in Japanese Patent Laid-Open No. 249,655/1987, the period of pressure pulses and the level of pressure are checked.
The output pressure from a driving apparatus varies, depending on the resistance of the pipeline between the driving apparatus and a blood pump, on the characteristics of the apparatus, and on the condition of the patient's circulatory system, such as the blood pressure or a cardiogram. Therefore, when the detected pressure is compared with a preset value, it is necessary to give a tolerence to the preset value. For this reason, it is impossible to accurately detect abnormal pressure. In the worst case, a driving apparatus operating normally is judged to be defective.